Cylindrical objects, such as containers and cans, are available in a variety of types and configurations. Two of the more common types are two-piece containers and three-piece containers. Two-piece containers are typically manufactured by a drawing and ironing process. In such processes a cup-shaped metal blank is drawn, optionally redrawn, then passed through successive ironing rings in order to lengthen and thin the sidewalls of the container. The open end of the two-piece container is then closed with a separate end piece. Three-piece containers are typically manufactured from metal roll stock that is cut into strips having a width that will substantially define the height of the resultant containers. Each strip is formed into a cylindrical shape and a longitudinal seam is established, e.g. by welding. The two open ends are then closed by attaching end pieces.
It is often desirable to alter the configuration of the sidewalls of cylindrical containers, including two-piece and three-piece containers, during the manufacturing process. For instance, the open end or ends of a container may be flanged in order to facilitate the attachment of end pieces. Additionally, the "necking-in" (i.e. reduction of diameter) of at least one end of the sidewalls of containers in order to reduce the material required for closing and sealing has become or is becoming standard practice for many container applications.
Another desirable configuration modification is the incorporation of one or more beads in the sidewalls of containers. Such beads can serve a number of useful functions, depending on their cross-sectional configuration and location on the sidewall.
For example, beads can increase the sidewall strength of a container, which is especially advantageous for containers fabricated from lightweight materials. As a result of the stronger sidewall, the container can withstand rough treatment in handling and transportation.
An outwardly projecting bead is also advantageous on containers having labels. For instance, if the outwardly projecting bead is placed at one or both ends of the container it can help prevent the label from sliding up or down along the longitudinal axis of the container. Additionally, by providing a recess for the label, the outwardly projecting bead can help protect the label when the container is rolled across a surface. These advantages can result in improved marketability and increased sales of the product packaged in the container.
Due to their method of manufacture, some containers will have different diameters at their two ends. For example, when a three-piece container is manufactured, it may have a flange and connected end piece at the bottom of the container which protrude laterally beyond the sidewall. On the other hand, the top flange and connected end piece may not laterally extend as far because the top may have been necked-in prior to flanging and attachment of the end piece. As a result of the different diameters at the two ends, the container will not roll straight on material handling equipment surfaces. An outwardly projecting bead placed near the top of the container can substantially equalize the diameters, thereby allowing the container to roll straight, easing and expediting the handling process.
It is known to form beads in a container sidewall by positioning opposing, mating die members adjacent to the interior and exterior surfaces of a container sidewall, and causing relative movement of the die members radially towards each other to bead the sidewall therebetween. For example, U.S. Pat. No. 4,487,048 by Frei et al. issued Dec. 11, 1984, discloses a method for beading the bodies of metal containers by rolling the container bodies between an inner tool and an outer tool, for instance, inner and outer mating rolls, in order to increase the container body sidewall strength. The inner tool has an expandable body and the container is rotated by rotating the inner tool after insertion and expansion within the container. The outer tool moves radially inward toward the inner tool to carry out the beading operation. Specifically, the outer tool is rolled upon the intermediately, radially inward disposed container body in order to force the container body to conform to the bead configuration of the mating surfaces.
It is believed that known beading methods have not been employed simultaneously with known container sidewall configuring processes which require relative axial (e.g. camming) movement between forming members positioned on opposing sides of a container sidewall. Additionally, it is believed that known beading devices cannot be successfully employed simultaneously or sequentially with such configuring processes to consistently form outwardly projecting beads at a desired location immediately adjacent to necked-in portions of container body sidewalls.
With particular respect to the present invention, it is known to vary the diameter of cylindrical objects, e.g. necking-in, by employing a spin forming process wherein the cylindrical objects are spun about their longitudinal axes while the sidewalls thereof are contacted by inner and/or outer forming members. U.S. Pat. No. 3,688,538 by Hoyne issued Sept. 5, 1972; U.S. Pat. No. 4,070,888 by Gombas issued Jan. 31, 1978; U.S. Pat. No. 4,563,887 by Bressan et al. issued Jan. 14, 1986; and U.S. patent application Ser. No. 858,774 by Bressan et al. filed May 2, 1986, now U.S. Pat. No. 4,781,047 issued Nov. 1, 1988, all disclose methods for necking-in cylindrical objects using spin forming methods. As indicated above, the necking-in of container bodies has or is becoming standard practice for many container applications. The above-referenced spin forming U.S. Pat. Nos. 4,563,887 and 4,781,047 are hereby incorporated by reference in their entirety. None of the spin forming references noted above disclose a method or apparatus for forming an outwardly projecting bead in the sidewall of a container before, during or after spin forming.
In view of the foregoing, it should be appreciated that it would be advantageous to consistently and reliably form outwardly projecting beads immediately adjacent to inwardly projecting, necked-in portions of container sidewalls. Further, it would be advantageous to form such outwardly projecting beads in the same operation during which the inwardly projecting, necked-in portions are formed. Additionally, it would be advantageous to form outwardly projecting beads in conjunction with a spin forming process.